The goal of the proposed project is to continue a research program employing the comparative approach to the study of the basel ganglia. The basal ganglia have long been a subject of scientific interest insofar as diseases of the basal ganglia such as Parkinsonism, chorea, athetosis, ballismus and torsion dystonia are considered major health problems. The focus of the proposed research is on the organization of the paleostriatal complexes of birds and reptiles. Five subsystems of the basal ganglia in these species are studied: (1) the ansal system, (2) the strio-tegmental system, (3) the ascending catecholamine systems, (4) the basal ganglia-tectal systems and (5) the intratelencephalic systems related to the basal ganglia. Special emphasis is placed on the organization of neurotransmitter systems within the basal ganglia pathways including the organization of the catecholamine, enkephalin and substance P systems. Previous research has indicated that the avian telencephalon is an excellent preparation for the study of basal ganglia-tectal and intratelencephalic systems related to the basal ganglia. Many of these advantages are also inherent in the use of reptilian preparations. Some work using rats is also in progress since aspects of the basal ganglia-tectal system of birds and reptiles suggested that similar pathways might exist in mammals.